drm/i915: don't queue PM events we won't process

On SNB/IVB/VLV we only call gen6_rps_irq_handler if one of the IIR
bits set is part of GEN6_PM_RPS_EVENTS, but at gen6_rps_irq_handler we
add all the enabled IIR bits to the work queue, not only the ones that
are part of GEN6_PM_RPS_EVENTS. But then gen6_pm_rps_work only
processes GEN6_PM_RPS_EVENTS, so it's useless to add anything that's
not GEN6_PM_RPS_EVENTS to the work queue.

As a bonus, gen6_rps_irq_handler looks more similar to
hsw_pm_irq_handler, so we may be able to merge them in the future.

v2: - Add a WARN in case we queued something we're not going to
      process.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net> (v1)
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -789,6 +789,9 @@ static void gen6_pm_rps_work(struct work_struct *work)
 	snb_enable_pm_irq(dev_priv, GEN6_PM_RPS_EVENTS);
 	spin_unlock_irq(&dev_priv->irq_lock);
 
+	/* Make sure we didn't queue anything we're not going to process. */
+	WARN_ON(pm_iir & ~GEN6_PM_RPS_EVENTS);
+
 	if ((pm_iir & GEN6_PM_RPS_EVENTS) == 0)
 		return;
 
@@ -959,7 +962,7 @@ static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv,
 	 */
 
 	spin_lock(&dev_priv->irq_lock);
-	dev_priv->rps.pm_iir |= pm_iir;
+	dev_priv->rps.pm_iir |= pm_iir & GEN6_PM_RPS_EVENTS;
 	snb_set_pm_irq(dev_priv, dev_priv->rps.pm_iir);
 	spin_unlock(&dev_priv->irq_lock);
 
@@ -1128,7 +1131,7 @@ static irqreturn_t valleyview_irq_handler(int irq, void *arg)
 		if (pipe_stats[0] & PIPE_GMBUS_INTERRUPT_STATUS)
 			gmbus_irq_handler(dev);
 
-		if (pm_iir & GEN6_PM_RPS_EVENTS)
+		if (pm_iir)
 			gen6_rps_irq_handler(dev_priv, pm_iir);
 
 		I915_WRITE(GTIIR, gt_iir);
@@ -1433,7 +1436,7 @@ static irqreturn_t ironlake_irq_handler(int irq, void *arg)
 		if (pm_iir) {
 			if (IS_HASWELL(dev))
 				hsw_pm_irq_handler(dev_priv, pm_iir);
-			else if (pm_iir & GEN6_PM_RPS_EVENTS)
+			else
 				gen6_rps_irq_handler(dev_priv, pm_iir);
 			I915_WRITE(GEN6_PMIIR, pm_iir);
 			ret = IRQ_HANDLED;